Due to their relative age, both AA and AF (we'll use these
abbreviations throughout the rest of the article) aren't necessarily en-vogue
features. Though most reviews include tests that have both
enabled, they're not necessarily the subject of in-depth investigations any
longer, contrary to how things were in the age of the original GeForce and the
VooDoo5, when AA was the hottest new arrival and AF was starting to become
somewhat interesting, with the original Radeon bringing high enough levels of
filtering, albeit at the cost of aggressive angle-dependency and the limitation
of it working only in tandem with bilinear filtering.

In this article, both of the aforementioned
techniques will be evaluated in-depth, and we'll attempt to show you how they
can improve the visual quality of your everyday gaming.

Anti-Aliasing

For starters, let's deal with AA, as that's arguably the
most noticeable of the dynamic duo, both in terms of its visual impact as well
as its ability to affect performance. For those technically oriented, this
Wikipedia article provides most
of the nitty-gritty details of what AA is, and what it tries to accomplish. In
layman's terms, AA is a technique through which the stair-step effect, known as
aliasing (there's a surprise, eh?), that is very apparent in-game along
polygon-edges is eliminated/reduced significantly. Aliasing is an artifact
resulting from the process of sampling and reconstructing a signal as an alias
of an original signal.

The first attempt at implementing AA in 3D games employed a
technique known as Supersampling, which basically involved rendering the image
at a higher resolution (2 times or 4 times as high, for 2X or 4X AA
respectively) and then downsampling the high resolution image. This was quite
costly in terms of fillrate, memory bandwidth and memory real-estate, and the
cards of the time lacked the resources required for making it a feasible option.

Multisampling

With the introduction of the Geforce3, the technique for
tackling AA that's been the preferred solution to this day came to the scene:
Multisampling. It was significantly more efficient, requiring that only the
depth value be supersampled, with other aspects such as color or stencil staying
at one evaluated value per pixel. Needless to say this reduced the fillrate and
bandwidth hits significantly as well as being less famished for VRAM, making
Multisampling a solid and desirable solution to the aliasing issue. Things have
been further optimized, with the introduction of color-compression and several
other tweaks, and today it seems that MSAA (Multisampling AA, another
abbreviation that'll be used from here on) will be with us for quite a while.

Another important aspect that has a major influence on the
effective quality of AA is the sampling pattern being employed. This refers to
the placement of the samples themselves around the pixel center (or centroid).
The Geforce3 used a rotated grid for 2X AA reverting to an ordered one for 4X
AA. Using an ordered grid is the worst case scenario in terms of effective
quality, as it has a number of sensitive angles at which the quality of AA is
reduced (some actually seemed to receive no AA at all). A rotated grid is
better, and the best case is using a sparse sampled grid in which no two samples
run along the same line.